Electric transformer



Nov. 10, 1931. RSCHARH 1,831,142

ELECTRIC TRANSFORMER Filed March 13, 1930 Inventor B Rudolf Scharli n II y 5 Attorney Patented Nov. 10, 1931 UNITED STATES PATENT OFFICE RUDOLFSCH ARLI, OF BADEN, SWITZERLAND, ASSIGNOR TO AKTIENGESELLSCHAFT BROWNROVER-I & CIR, OF BADEN, SWITZERLAND, A JOINT-STOCK COMPANY OFSWITZERLAND ELECTRIC TRANSFORMER Application filed March 13, 1930,Serial No. 435,383, and in Switzerland March 28, 1929.

This invention relates to electric current transforming apparatus and,particularly, to single phase or polyphase step-up transformers withconcentric coils.

\Vhen a polyphase transformer with three or more concentric coils oneach core leg is used for the transformation of voltages from a currentsource to two or more supply networks, the concentric coils usually havethe disadvantages that at least two of the wind ings have a very smallreactance which greatly endangers the safety of the transformer againstshort circuit, or they have a very large reactance, which causes a highvoltage drop in the transformer. One method by which the abovedisadvantages may be avoided is by dividing one of the windings intohalf portions, and arranging the half portions concentrically with theother windings, thereby giving four concentric windings. Suchconstruction, however, makes the calculation of the reactance of theseveral windings difiicult, and likewise makes the construction morediflicult and expensive. The use of four concentric coils naturallyincreases the size of the tank which can be used, and therefore requiresa greater amount of space than is available under many conditions.

With the foregoing in mind, it is an object of the present invention toprovide a single phase or polyphase transformer in which at least two ofthe coils are divided into two or more sections arranged and connectedin such manner that each coil comprises coil sections of two or moredifferent diameters.

Other objects and advantages will be apparent from the followingdescription when read in connection with the annexed drawing, whichshows one embodiment of the present invention with the coils shown incross-section.

Referring more particularly to the drawing by characters of reference,the reference numeral 1 indicates a core member of magnetic material, asis usual, and the reference numeral 2 indicates the inner windingarranged directly about the core member.

The outer winding comprises the coils 3 and 4., each coil being divided,as shown, into alon the core le sections of difierent diameters arrangedThe larger section of coil 3 is disposed about and is concentric to thesmaller section of coil 4, while the larger section of coil 4 isdisposed about and is concentric to the smaller section of coil 3. Therespective sections of the coils 3 and 4 are connected in series, asshown. This arrangement and manner of connection provides that thereactance of coil 3 is substantially equal to that of coil 4:.

The coil 2 may, if desired, be divided and inter-connected in likemanner so that the reacta ice of all of the coils may be entirelybalanced. It will be apparent that coils 3 and 4, as well as additionalcoils, may be divided into two or more sections of two or more diiferentdiameters, and may be connected in such manner as to obtain pairs ofidentical coils arranged symmetrically with respect to the core member.It is immaterial whether the coils are arranged exactly concentricallywith the core or eccentrically with the core, so long as the coils aredivided and inter-connected to make the reactance of the several coilsapproximately equal.

Although but one embodiment of the present invention has beenillustrated and described, it will be apparent that various changes maybe made therein without depart-ing from the spirit of the invention orfrom the scope of the appended claims.

The invention claimed is:

1. In a transformer, a core, and coils disposed about said core, each ofsaid coils divided into sections of different diameters arranged alongthe core, a section of one coil disposed about a section of anothercoil.

2. In a transformer, a core, a winding dis-.

RUDOLF SCHARLI.

